This invention relates in general to vehicle disc brake assemblies and in particular to an improved structure for an electric parking brake actuator for use in such a disc brake assembly.
Most vehicles are equipped with a brake system for slowing or stopping movement of the vehicle in a controlled manner. A typical brake system for an automobile or light truck includes a disc brake assembly for each of the front wheels and either a drum brake assembly or a disc brake assembly for each of the rear wheels. The brake assemblies are actuated by hydraulic or pneumatic pressure generated when an operator of the vehicle depresses a brake pedal. The structures of these drum brake assemblies and disc brake assemblies, as well as the actuators therefore, are well known in the art.
A typical disc brake assembly includes a brake rotor which is secured to a wheel of the vehicle for rotation therewith. The disc brake assembly further includes a caliper assembly that is slidably supported on pins secured to an anchor bracket. The anchor bracket is secured to a non-rotatable component of the vehicle, such as the axle flange or steering knuckle, which is connected to the vehicle frame. The caliper assembly includes a pair of brake pads which are disposed on opposite sides of the brake rotor. The brake pads are connected to one or more hydraulically or pneumatically actuated pistons for movement between a non-braking position and a braking position, wherein they are moved into frictional engagement with the opposed braking surfaces of the brake rotor. For example, when an operator of the vehicle depresses the brake pedal, the piston urges the brake pads from the non-braking position to the braking position so as to frictionally engage the opposed braking surfaces of the brake rotor and thereby slow or stop rotation of the associated wheel of the vehicle.
The disc brake assembly may also include an electromechanical actuating device that is used to realize a parking brake function of the disc brake assembly. The electromechanical actuating device may comprise a rotationally restrained nut threaded onto a motor driven spindle. As the spindle is rotationally driven, the nut axially translates to move the piston and urge the brake pads between the braking and non-braking positions. The piston may be hollow with the nut and spindle located inside the piston. However, the electromechanical actuating device may produce an undesirable noise or rattle from the nut contacting and/or moving the piston. Therefore, it would be desirable to reduce or minimize any noise or rattle in the electromechanical actuating device for the disc brake assembly.